Proposal of Numerical Method to Evaluate the Effects of Landslide Prevention Works

利用极限平衡法对水平排水沟、桩、锚杆等滑坡防治工程进行了设计。然而，已知LEM不能正确考虑问题的三维效应以及土体与防渗工程之间的相互作用，而FEM可以很容易地考虑这些。基于饱和-非饱和渗流有限元法和考虑抗剪强度折减技术的弹塑性有限元法，对这些防渗工程的效果进行了分析。结果表明，采用三维整体安全系数对加固边坡的效果进行了评价。其中一种提出的方法已被应用于发生在日本群马县的一次真正的巨大滑坡。在非饱和-饱和土渗流有限元分析的基础上，进行了排水井的优化定位，为滑坡防治措施的创新和经济设计提供了依据。

The design of landslide prevention works such as horizontal drains, piles and anchors has been conducted based on the limit equilibrium methods. However, it is known that the LEM can not correctly consider the 3D effects of the problems and the interaction between soils and prevention works, which can be easily taken into consideration by FEM. The effects of these prevention works are analyzed based on the saturated-unsaturated seepage FEM and the elasto-plastic FEM that considers the shear strength reduction technique. It is shown that the effects are evaluated by the 3D global safety factor of slopes reinforced with these prevention works.One of these proposed methods has been applied to a real huge landslide which occurred in Gunma, Japan. The optimal positioning of drainage wells was performed analytically based on the finite element analysis of water flow through unsaturated-saturated soils, which lead to an innovative and economical design of prevention measures for the landslide.